Feeling unwanted

I’m 17 and in an all girls school and I sit with the same group of girls everyday at lunch. Last year everything was great we could have a laugh and just say anything without caring but I feel like it’s different now and I’m not sure why it’s changed🙄 I’m almost positive one of the girls in my group doesn’t like me, everytime I say something she just ignores it and she goes out of her way to exclude me from things we’re talking about. I don’t know why since I’ve never done anything to her ?? I always am friendly with her and smile when I see her but she kind of just brushes it off, I feel so annoying and unimportant when she’s around☹️ she wasn’t always like this that’s why I notice it so much and I don’t know what to do, I can’t say it to my other friends because I don’t want to put them in an awkward position but I’m not sure why she’s so rude to me all of the time it just makes school less enjoyable for me and I hate feeling like the least important of the group